Known as Scribbles, the software enables the embedding of "Web beacons" or watermarks in Word documents so that they can be tracked down in the event of being stolen.

The version released (v1.0 RC1) is dated March 2016 and classified SECRET//ORCON/NOFORN until 2066. The accompanying documentation advises that this release candidate is not to be deployed, adding that end to end developer testing has been completed on Windows 8.1 with Microsoft Office Professional Plus 2013.

This is the seventh drop that WikiLeaks has made from what it has chosen to call Vault 7, beginning on 7 March.

The documentation says: "Scribbles (SCRIB) is a document watermarking tool that can be used to batch process a number of documents in a pre-seeded input directory. It generates a random watermark for each document, inserts that watermark into the document, saves all such processed documents in an output directory, and creates a log file which identifies the watermarks inserted into each document."

It says the tool was successfully tested on Office 2013 (on Windows 8.1 x64), documents from Office versions 97-2016 (Office 95 documents will not work!) and documents that are not locked forms, encrypted, or password-protected.

There is a limitation to the Scribbles system: if a document that has the watermarks in it and is opened in OpenOffice, LibreOffice the watermark images and URLs may become visible.

The documentation advises: "For this reason, always make sure that the host names and URL components are logically consistent with the original content. If you are concerned that the targeted end-user may open these documents in a non-Microsoft Office application, please take some test documents and evaluate them in the likely application before deploying them."